1. Field of the Invention
The invention relates, generally, to pressure regulators and, more specifically, to a proportional pressure regulator having the capability to deliver both negative and positive pressure, as well as providing a system exhaust.
2. Description of the Related Art
Pressure regulators are well known in the art and are employed in numerous environments to regulate a pneumatic supply pressure down to a predetermined system pressure. The system pressure is then supplied to operate various pneumatically actuated devices. In the past, a regulated system pressure was achieved through the use of a purely mechanical arrangement within the regulator, often with the assistance of a pressure feedback line returned to the regulator from the output side.
Some types of pneumatic systems still utilize mechanical regulators where course regulation and/or large volume pneumatic control is involved. However, where accuracy and fine regulatory control of pneumatic system pressure is required, regulators have rapidly evolved. The current state of the art provides pressure regulators that include an electrically controlled actuator, most often a solenoid, to regulate the output pressure. Pressure feedback is also utilized for more responsive control. In this case, a transducer may be employed to sense pressure and convert it to an electrical signal that is used by a feedback control circuit to assist in regulating the output. In this manner, the system pressure is regulated about a predetermined setpoint using feedback measurements from the particular process involved or the downstream output pressure.
Regulators of this type are well known and are sometimes referred to in the related art as proportional pressure regulators. The term xe2x80x9cproportionalxe2x80x9d is used in the sense that if a difference is measured between a desired predetermined output setpoint and the actual downstream pressure, then the regulator changes, and thereby controls, the output pressure in xe2x80x9cproportionxe2x80x9d to that difference. Refinements in proportional regulators have included the use of digital circuits that have the capability to employ sophisticated control algorithms to more precisely control the regulator. The proportional pressure regulators with digital electronic control circuits use the feedback signal to electronically determine a difference or xe2x80x9cerrorxe2x80x9d between the desired output pressure setpoint and the actual output pressure.
More sophisticated digital control circuits use a control algorithm along with other system inputs to generate an overall control or scheme that operatively controls the regulator to adjust, or vary, the output pressure in an attempt to resolve the xe2x80x9cerrorxe2x80x9d and return the output to the predetermined setpoint. These known digital control schemes often employ complex calculations for error resolution, as evidenced in U.S. Pat. No. 6,178,997 B1 to Adams et al, which discloses an xe2x80x9cIntelligent Pressure Regulatorxe2x80x9d. The Adams ""997 regulator has a PID (proportional-integral-derivative) controller that calculates the mathematical integral and derivative of the proportional error and employs the results of these calculations in its control algorithm. A PID controller uses the current value of the error to calculate both the integral of the error over a recent time interval, and the current derivative of the error signal. The PID controller then sums the error with the results of these calculations to determine not only the required amount of adjustment necessary, but also the duration of the adjustment to avoid overshoot of the setpoint.
Proportional pressure regulating devices have evolved to include regulating systems for advanced applications that require complex pressure sensing and monitoring, and equally complex regulating schemes. These pressure regulating systems have the capability to not only produce an accurate regulation of a constant predetermined setpoint, but to also respond to system sensors and dynamically vary the pressure setpoint and regulate the system pressure to it, even as the setpoint changes during the operation of the process. For example, regulator systems of this type may be employed in connection with devices used to polish the surface of semiconductor wafers. A polishing pad is pneumatically controlled so as to apply a predetermined force to the surface of the semiconductor wafer during the polishing process. In these circumstances, it is desirous to maintain a certain predetermined downward force of the polishing device to the wafer surface, while countering various dynamic physical effects that make the applied downward force a constantly varying value.
In some other particular processes and working environments, it is further desirable to have a pressure regulating system that not only has variable setpoint proportional regulation for control of system pressure in a positive pressure range, as described above, but one that also has variable setpoint proportional regulation to control system pressure in the negative (vacuum) pressure range. For some processes, this can offer greater accuracy of pneumatic control by providing a variable pressure setpoint of the system pressure that can be readily moved between positive and negative supply pressures for any given active device. For example, the highly precise manufacturing process involving the polishing of silicone wafers for use as integrated circuit chips, as well the polishing processes for disk media, such as CDs, DVDs, and the like, often use both negative and positive regulated pressures to operate and control the various precision mechanisms involved. U.S. Pat. No. 5,716,258 to Metcalf and U.S. Pat. Nos. 6,203,414 and 6,319,106 to Numoto disclose devices for use in silicone wafer polishing processes that rely on variable and precisely regulated positive and negative pressures to provide extremely fine control of the polishing procedure.
In applications such as these, the pressure regulating system must control each active pneumatic component in both positive and negative pressures. Systems known the related art require separate proportional regulator valves to effect control in both positive and negative pressures. The separate proportional regulators are each distinct and are selectively employed remote from one another. Thus, for each active pneumatic device, the separate regulators must be incorporated at various positions relative to one another in the system and must be interconnected via conduits or other flow passages. Additionally, the positive and negative regulators each have a separate electronic control circuitry, operatively connected to each other, to coordinate the positive and negative pressure regulating functions. While these separate components have generally worked well in the past, there remains an ongoing need in the art to simplify pneumatic systems and thereby lower costs of manufacture and/or assembly by eliminating separate components, shortening flow paths and thereby reducing related hardware.
The disadvantages apparent with the conventional complexity of these positive and negative pressure regulated systems are further compounded when efforts have been made to increase the accuracy in these systems. Specifically, while variable setpoint proportional regulation of the positive and negative system pressures is an effective control means for some process applications, the response times and accuracy of control can be further enhanced by additionally providing an exhaust, or vent capability to the pneumatic regulating scheme.
U.S. Pat. No. 6,113,480 to Hu et al discloses a wafer polishing apparatus that uses negative and positive pressure with an exhaust vent to control the polishing procedure. The use of an exhaust vent, as in the Hu ""480 patent, decreases the response time of the pneumatic regulating circuit by providing a rapid and almost instantaneous reduction or complete removal of the supplied pressure when needed. This allows for very fast control changes from one pressure to the other, as in the case of changing from a regulated positive pressure to a negative pressure, or vice versa. Thus, the controlled pneumatic devices can be more accurately and finely controlled in precision operations.
The exhaust vent is also useful when it is necessary to proportionally decrease, but not reverse, the applied pressures. In these cases, whether the controller is varying the setpoint or regulating pressure, actuating the exhaust vent will rapidly drop the applied pressure to the desired level, rather than having to merely rely on the pressure to fall off by itself when the applied pressure is proportionally decreased. This function maybe employed in connection with both the positive and the negative proportional pressure regulation.
Regardless of how an exhaust vent is employed in conjunction with these regulators and regulating systems, when used with a sophisticated and complex process, such as shown in the Hu ""480 patent, these systems must still utilize numerous separate components, hardware and support elements of their non-vented counterparts. Therefore, despite the great improvements in accuracy and efficiency in pneumatic pressure regulating systems presently known in the related art, they remain highly complex assemblies. In fact, the systems that employ the variable setpoint proportional pneumatic regulation devices mentioned above require so many associated components and hardware that their complexity and size often becomes a limiting factor in their application. Thus, there remains an ongoing need in the art to simplify these proportional pneumatic pressure regulator systems, to lower costs of their manufacture and/or assembly by eliminating separate components, to reduce related hardware and to shorten the inherently lengthy flow paths commonly employed in the regulator systems known in the related art. Furthermore, there remains a need in the art for a regulator system that employs a control circuitry that can effectively, efficiently, and accurately control positive pressure, negative pressure, and venting functions of an integrated regulating system.
The present invention overcomes the disadvantages of the related art in a proportional pressure regulator assembly having a main body with a first inlet adapted for fluid communication with a supply of positive pneumatic pressure, a second inlet adapted for fluid communication with a supply of negative pneumatic pressure, at least one outlet adapted for fluid communication with at least one pneumatically actuated device, and an exhaust port. A fill regulator valve is provided that is in fluid communication with the first inlet port and the outlet and that is adapted to regulate the supply of positive pressure to a predetermined value from the first inlet to a pneumatically actuated device when the fill regulator valve is actuated. A vacuum regulator valve is provided that is in fluid communication with the second inlet port and the outlet and that is adapted to regulate the supply of negative pressure to a predetermined value from the second inlet to a pneumatically actuated device when the vacuum regulator valve is actuated. An exhaust valve is provided that is in fluid communication with the outlet and is operable to exhaust pressure from the outlet when the exhaust valve is actuated. Therefore, the proportional pressure regulator of the present invention combines and centralizes all the functions of existing systems into a single integrated assembly thereby reducing the number of components and simplifying the overall structure.
The proportional pneumatic pressure regulator assembly of the present invention also overcomes the drawbacks of conventional regulation systems by providing a control circuit assembly that is adapted to receive a command signal and actuate either the fill regulator valve, the vacuum regulator valve, or the exhaust valve to dynamically set the output pressure at a specific value, or setpoint, in response to the command signal. The control circuit assembly is further adapted to receive a feedback signal and regulate the amount of positive pneumatic pressure through the fill regulator valve and the amount of negative pneumatic pressure through the vacuum regulator valve about the desired setpoint in response to the feedback signal. The proportional pressure regulator of the present invention provides a centralized electronic control for the regulation of positive, negative, and exhaust pressures, thereby eliminating the individual controls of conventional systems and their associated components.
Thus, the proportional pressure regulator of the present invention includes an integrated regulator assembly which provides either a positive pressure, a negative pressure, or exhaust venting functions. In addition, the present invention is directed toward a proportional pressure regulator assembly having a control circuit assembly that dynamically establishes a variable output setpoint in response to a command signal while proportionally regulating the output pressure about the setpoint in response to a feedback signal. This capability has application in a number of industrial settings where providing a combination of positive pressure, negative pressure, and exhaust capability with accurate regulation are critical to the highly accurate control of the production process. For example, the extreme accuracy required in the manufacture and polishing of silicon wafers for the production of integrated circuits or the production and polishing ofdisk media, such as hard drive disks, CD-ROMS, and DVDs all require systems that can provide positive pressure, negative pressure, and exhaust venting along with precise control. The present invention is highly advantageous in these or similar environments where its integrated design simplifies the complex pneumatically actuated systems and allows for smaller, more tightly integrated assemblies, ease of maintenance, and reduced costs. In this way, the proportional pressure regulator assembly of the present invention results in increased efficiency, accuracy, and cost savings in the production process.